The present invention relates to a fuel system for a motor vehicle with a fuel container from which a fuel pump transports fuel via fuel pipelines from a system input location in the fuel contain via a fuel filter towards a motor.
Fuel systems for motor vehicles are already known in which a fuel filter is provided, where the fuel filter can be installed inside and/or outside a fuel container. The fuel flow through these filters is only ever in one direction. Because of this, the dirt contained in the fuel is increasingly deposited over time on the inflow side of the filter. If there is a large amount of dirt in the fuel, a filter cake can form which leads to an increase in throughflow resistance. This means that the demands on the performance of the fuel pump within the fuel system also increase.
This aim of the present invention is to create a fuel system for a motor vehicle in which the throughflow resistance does not increase over the lifetime of the vehicle or increases only relatively slightly.
This aim is fufilled by a deposition tank formed into a housing of the fuel filter under a filter material provided in the housing into which dirt filtered out of the fuel is deposited and a pressure accumulator is installed in the fuel system which after the motor is switched off, the fuel stored in the pressure accumulator rinses the fuel filter.
The fuel system according to the invention exhibits a fuel filter in which a deposition tank is provided. In addition a pressure accumulator is built into the system in such a way that the fuel which is in the pressure accumulator is depressurized after the engine has been switched off and rinses the filter from the fuel outlet side or clean side toward the fuel inlet side or dirt side. By these means the advantage is created that dirt which has collected on the fuel inlet side is released from the filter and collects in the deposition tank.
The deposition tank of the present invention is advantageously formed by means of the structure of the housing, for example by the provision of guide vanes, in such a way that fuel does not flow through the deposition tank and therefore the deposited dirt is not disturbed.
The fuel filter according to the invention can advantageously, be located on either the pressure side or the suction side within the fuel system, in other words, behind or in front of the fuel pump.
In an advantageous embodiment, with the fuel filter located on the pressure side a pressure accumulator is installed in the direction of the engine after an outlet opening of the filter housing, and with the fuel filter located on the suction side after an outlet opening of the fuel pump, and in both cases is installed in front of a pressure regulator with an upstream non-return valve. The positioning of a non-return valve between a branch point leading to the pressure accumulator and the pressure regulator prevents the fuel pipeline to the motor from emptying.
In an advantageous embodiment a delay valve is provided in the fuel system in order that filling of the pressure accumulator does not influence the buildup of pressure in the fuel system after the engine has been started.
The fuel system which is the subject of the present invention is particularly advantageous in that the fuel filter achieves a longer lifetime. A further advantage is that by means of the structure of the fuel filter as embodied in the invention, the filter volume can be decreased in comparison with a known fuel filter while maintaining the same lifetime.
Because the fuel filter is cleaned each time the engine is switched off, the volume throughflow resistance of the fuel filter remains approximately constant. Therefore, the fuel pump of the fuel system only needs to exert normal pressure and not increased pressure as is the case with a blocked fuel filter, so that the lifetime of the fuel pump is higher in comparison with fuel systems with traditional fuel filters.
A further advantage is that the fuel filter, the pressure regulator, the fuel pump, the non-return valve, the pressure accumulator and possibly the surge chamber can be implemented in the form of a preassembled unit, and therefore the emissions are also less.